spring 事件机制笔记

注册监听器
AbstractApplicationContext refresh()

private void registerListeners() throws BeansException {
		// Do not initialize FactoryBeans here: We need to leave all regular beans
		// uninitialized to let post-processors apply to them!
		Collection listeners = getBeansOfType(ApplicationListener.class, true, false).values();
		for (Iterator it = listeners.iterator(); it.hasNext();) {
			addListener((ApplicationListener) it.next());
		}
	}

public class SimpleApplicationEventMulticaster extends AbstractApplicationEventMulticaster {

	private TaskExecutor taskExecutor = new SyncTaskExecutor();


	/**
	 * Set the TaskExecutor to execute application listeners with.
	 * <p>Default is a SyncTaskExecutor, executing the listeners synchronously
	 * in the calling thread.
	 * <p>Consider specifying an asynchronous TaskExecutor here to not block the
	 * caller until all listeners have been executed. However, note that asynchronous
	 * execution will not participate in the caller's thread context (class loader,
	 * transaction association) unless the TaskExecutor explicitly supports this.
	 * @see org.springframework.core.task.SyncTaskExecutor
	 * @see org.springframework.core.task.SimpleAsyncTaskExecutor
	 * @see org.springframework.scheduling.timer.TimerTaskExecutor
	 */
	public void setTaskExecutor(TaskExecutor taskExecutor) {
		this.taskExecutor = (taskExecutor != null ? taskExecutor : new SyncTaskExecutor());
	}

	/**
	 * Return the current TaskExecutor for this multicaster.
	 */
	protected TaskExecutor getTaskExecutor() {
		return taskExecutor;
	}

广播事件

public void multicastEvent(final ApplicationEvent event) {
		for (Iterator it = getApplicationListeners().iterator(); it.hasNext();) {
			final ApplicationListener listener = (ApplicationListener) it.next();
			getTaskExecutor().execute(new Runnable() {
				public void run() {
					listener.onApplicationEvent(event);
				}
			});
		}
	}

}

FrameworkServlet

this.webApplicationContext.publishEvent(
						new ServletRequestHandledEvent(this,
								request.getRequestURI(), request.getRemoteAddr(),
								request.getMethod(), getServletConfig().getServletName(),
								WebUtils.getSessionId(request), getUsernameForRequest(request),
								processingTime, failureCause));

具体的事件处理

public class PerformanceMonitorListener implements ApplicationListener {

	protected final Log logger = LogFactory.getLog(getClass());

	protected final ResponseTimeMonitorImpl responseTimeMonitor = new ResponseTimeMonitorImpl();


	public void onApplicationEvent(ApplicationEvent event) {
		if (event instanceof RequestHandledEvent) {
			RequestHandledEvent rhe = (RequestHandledEvent) event;
			this.responseTimeMonitor.recordResponseTime(rhe.getProcessingTimeMillis());
			if (logger.isTraceEnabled()) {
				// Stringifying objects is expensive. Don't do it unless it will show.
				logger.trace("PerformanceMonitorListener: last=[" + rhe.getProcessingTimeMillis() + "ms]; " +
						this.responseTimeMonitor + "; " + rhe.getShortDescription());
			}
		}
	}

}